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    <title>Document</title>
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    <script>
        let ary = [1,2,3,4,5,6,7,8];
        let newAry = ary.map(function(item){
            if(item % 2 == 0){
                return item * 10;
            }else{
                return item;
            }
        });
        console.log(newAry);
        let newAry1 = ary.filter(function(item){
            if(item % 2 == 0){
                return item;
            }
        });
        console.log(newAry1);

        let newAry2 = ary.reduce((a,b) => {
            console.log(123);
            return a + b;
        });
        console.log(newAry2);
    </script>
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